Positive selection for colicin diversity in bacteria

• Published in: Molecular biology and evolution Vol. 10; no. 5; pp. 1048 - 1059
• Main Author: RILEY, M. A
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.09.1993
• Subjects: Bacteria - genetics; Bacteriocin Plasmids - genetics; Bacteriology; Biological and medical sciences; Colicins - genetics; Escherichia coli - genetics; Fundamental and applied biological sciences. Psychology; Genes, Bacterial; Genetic Variation; Genetics; Microbiology; Recombination, Genetic; Selection, Genetic; Colicin; Molecular evolution; Divergence; Gene; Nucleotide sequence; Escherichia coli; Bacteria; Chromosome DNA; Disruptive selection; Enterobacteriaceae; Natural selection
• ISSN: 1537-1719; 0737-4038; 1537-1719
• DOI: 10.1093/oxfordjournals.molbev.a040054

To examine the hypothesis that colicin proteins are subject to diversity-enhancing selection, we studied the rates of synonymous, nonsynonymous, and intergenic nucleotide substitution in three pairs of closely related colicin clusters. The results indicate that the immunity gene and the immunity-binding domain of the colicin gene, which interact to provide specific immunity from the lethal action of the colicin toxin, accumulate substitutions at synonymous and nonsynonymous sites several times more rapidly than does the remainder of the colicin cluster. We suggest that this increased level of divergence, centered at the immunity protein, may be the result of the combined action of recombination and positive selection acting to increase colicin diversity in natural populations of Escherichia coli.